Safety burner control and ignition switching mechanism for providing a purging period



NOV. 13, H c, NYCUM ETAL SAFETY BURNER CONTROL AND IGNITION SWITCHING MECHANISM FOR PROVIDING A PURGING PERIOD Filed Sept. 15, 1947 Patented Nov. 13, 1951 ssm-z'rr comma CONTROL AND IGNITION swrrcnmo mncnsmsm son rnovmmc A ruacmo rnnron Homer 0. Nycum and Clyde 0. Baird, Kalamazoo. Mich., assignors tov The C. H. Dutton Company, Kalamazoo, Mich., a corporation of Michigan Application September 15, 1947, Serial No. 774,182 g Claims. (01. 158-28) This invention relates to improvements in a boiler control system.

The principal objects of this invention are:

First, to provide a system of controls for gaseous or liquid fuel burners particularly for boiler furnaces and the like in which the burner cannot be started while there is a dangerous accumulation of fuel in the furnace.

Second, to provide a control system for the burner element of a boiler in which an ignition means is actuated by cycling mechanism arranged to provide a pre-ignition purging period to remove any accumulation of fuel of an explosive character from the furnace before applying the ignition.

Third, to provide a control system for boiler burners and the like which is adaptable to various cycles of operation such as single ignition or automatic repeated ignition depending upon the desired method of operating the boiler.

Fourth, to provide control circuits for starting and igniting the burner mechanism of a boiler in which manual operation of any of the switches in the circuit cannot immediately apply ignition energy to the burner but must first initiate automatic cycling mechanism which in turn will ignite the burner.

Fifth, to provide a control circuit for a boiler or the like in which an alarm or other device indicating the necessity for manual attention may be arranged to be actuated under a plurality of different operating conditions depending upon the desired cycle of operation of the boiler.

Sixth,'to provide cyclically operating starter mechanism for a burner arranged to require a complete purging cycle before it will apply ignition energy to the burner so that if the mechanism is de-energized during its purging or ignition periods it will have to return to its starting position before again being effective to start the burner.

Seventh, to provide a cycling starter mechanism for a burner with a transfer device arranged to remove the control of the burner from the starter mechanism should the starter mechanism be deenergized during its cycle of operation so that upon re-energization of the starter mechanism it will complete its unfinished cycle before being effective to start the burner.

Eighth, to provide a control circuit for the burner of a boiler or the like which positively eliminates the chance of an explosion in the furnace.

Other objects pertaining to the details and advantages of the system will be apparent from a consideration of the following description claims.

'ine drawings, of which there is one sheet, illustrate two arrangements of our control system as applied to the burner and auxiliary elements of a boiler.

Fig. l is a schematic diagram of our control circult and showing the auxiliary elements of the boiler conventionally.-

Fig. 2 is a schematic wiring diagram of a sec and mm of our control circuit and showing the auxiliary elements of the boilerconventionally,

In the form of our inventionillustrated in Fig. 1, we have conventionally shown several of the auxiliary controls and elements which are common to most boilers and boiler burners. We have not attempted to show the boiler or burner asit will be understood that these elements will be associated with a boiler in the usual manner.

A water level switch is indicated at l and pressure switch at 2. The pressure switch is arranged to open when pressure in the boiler rises above a predetermined value and the water level switch I is arranged to open when the water in the boiler falls to a dangerous level. The switches I and I may be referred to as primary control switches and are connected in series in one side of a power source indicated at 3. For convenience this side of the power source may be referred to as the live side. A manually operated main breaker switch is indicated at 4 and a manually operated shut down switch for the boiler is indicated at i. A motor for driving a draft or exhaust fan (not shown) for the boiler is illustrated at 6 and is connected directly across the power source but in series with the switches l, 2, l and 5.

An ignition device for the burner of the boiler is indicated at 1. This may be any accepted form of ignition device, the one shown being a spark gap with the necessary transformer for providing high voltage ignition energy. A solenoid controlled valve 8 is provided for admitting a light oil or gas as primer fuel during the operation of the ignition device.

The mechanism for obtaining separate purging and ignition periods in this form of the invention comprises a cam shaft 9 driven through the vworm and gear l0 from the timer motor I I. The

cam shaft 9 is provided with a lock-out cam I2 having a substantially continuous surface broken by the look-out recess I3. The cam shaft is also provided with an ignition cam it having an inntion energizing surface [5. The lock-out recess l3 and ignition energizing surface 15 are angularly displaced with respect to each other so that when the cam shaft is rotated in the direction indicated by the arrow, the ignition, energizing surface will engage the switch arm ii to close contact ll, prior to engagement of the switch arm [8 with the lock-out notch l3 and to hold the contact ll closed until just before the arm 18 has re-engaged in the look-out notch 13 to disengage the contact I! from the conductor 20 and stop the motor H with the contact I9 engaged with the conductor 2 l The controls in Fig. l are illustrated in the same position they will assume if the breaker switch 3 and shut down switch 5 are opened, as shown, while the cycling mechanism is in the middle of an ignition or lighting cycle.

The timer motor is arranged to be energized from the dead side of the line through the conductor 22 and normally open push button 23 to the live side of the line. A holding circuit consisting of the conductor 20 and contact l9 mounted on the switch arm [8 is provided so that the push button 23 does not need to be held closed throughout the entire ignition period. It should be evident that once the timer motor H has been started to rotate the look-out cam 12, the arm 18 will be raised to bring the contact I! into engagement with the conductor 20 so that the timer motor will continue to operate without holding the push button closed until the cam shaft has made one complete revolution and i e-engaged the look-out notch 13 with the switch arm [8.

In the lowered or lock-out position of the switch arm la, the under side of the contact I3 is connected to the conductor 2!, extending to a flame control switch 24. The flame control switch may be of several different forms arranged to respond to the presence of the main flame in the furnace. The example illustrated consists of a bimetallic element having a lower contact 25 and an upper contact 25 insulated therefrom. The contact 25 is arranged to connect the conductor 2| to the conductor 21 when the flame is extinguished. Establishment of the flame in the furnace causes the contact 26 to be engaged with the conductor 28. Contact 26 is connected to the wire 29.

One branch of the conductor 21 extends to the alarm bell 30 while another branch extends to the terminal 3| arranged to be connected to the conductor 32 in the deenergized position of a safety relay indicated in its entirety by the letter T. The conductor 32 extends to the solenoid of the relay T and is arranged to energize the solenoid either through the terminal 3| and con ductor 21 or through the conductor 29 connected through the contact N to the live side of the line.

From the above description, it will be apparent that with the look-out notch I3 in engagement with the switch arm l8 upon closing of the primary switches, -a circuit will be established through the solenoid of relay '1, conductor 32, terminals 3|, conductor 21, flame control switch 20, and contact l9 to energize the relay T. Energization of the relay T immediately opens the terminals 3|, sealing the solenoid to the lines through the conductor 29 and making a connection between the terminals 33. 1

The burner motor of the system is conventionally illustrated at 34, and is connected in parallel with the solenoid operated main fuel valve 35 to a conductor 36 provided with terminals 31 positioned on each side of a contact 33, operated by a transfer relay indicated in its entirety by the letter R. The solenoid of relay R is arranged to be energized from the dead side of the line through the conductor 28 to the upper contact 26 of the flame control switch 24, contact 26 being insulated from contact 25. Thus.

when a flame is established in the furnace and the switch arm It moves tclock-out position, a running circuit for the burner motor and main fuel valve will be established through the contact 26, conductor 28, contact 31, and conductor 38. Failure of the flame for any reason will open the contact 26, de-energizing both the solenoid of relay R. and the burner motor and main fuel valve 35.

' In the de-energized position of the relay R, the conductor 36 is connected through one of the terminals 31 to a conductor 88, extending to one of the terminals 33 on the relay T. Thus, before a flame has been established in the furnace to close the contact 26 and upon closing of the ignition contact ll, a circuit will be established from the burner motor and main fuel valve concurrently with the circuit to the ignition device I and primer fuel valve 8. This condition will exist through the engagement of the ignition surface l5 with the switch arm Hi. If a flame is properly established in the furnace during the ignition period, determined by the length of the ignition surface i5, the burner motor and main fuel valve will continue to be energized through the previously described circuit controlled by the flame operated switch 24. Otherwise, the burner motor and main fuel valve will be deenergized along with the ignition device I by opening of the contact H as the cam shaft nears the end of its rotational cycle and just before the engagement of the switch arm l8 with the look-out recess l3.

The normal shut down position of the circuit shown in Fig. 1 is with the several relay switches in the position shown, but with switch arm 18 engaged with, the look-out recess l3 and the contact [9 in engagement with the conductor 2|. The switch arm IE will be raised opening the contact I! so that all elements of the system will be de-energized. Upon closin the power switches 3 and 5, a circuit will be established through the conductors 2i and 21 and flame operated switch 24 to energize alarm 30 and solenoid relay T. The relay T will immediately transfer itself to the holding conductor 29 and close the terminals 33 but the circuit to the burner motor, ignition device and fuel valves will remain open at the contact IT. The operator may then close the push button 23 to energize the timer motor II, as previously described. The timer motor will rotate the cam shaft through a single cycle opening the connection to the conductor 21 and silencing the bell and after a purging period, determined by the length of the raised portion of the ignition cam, will energize burner motor, ignition device and fuel valves. If the ignition attempt is successful the system will come to rest with the flame burning, and with the burner motor and main fuel valve energized, as previously described, through the conductor 28.

A subsequent failure of the flame for any reason will open the contact 26, stopping the burner motor and closing the contact 25, sounding the alarm which will continue ringing until a re-light attempt is made by manual operation of the button 23. With the system just described, it is impossible to apply fuel and ignition energy to the burner before a complete purging period, as determined by the ignition cam H. Closing of the push button 23 does not apply r ignition energy-but merely sets in motion the cycling mechanism to automatically apply ignition after a full purging period. Even though the system may be shut down as by opening the power switches 3 and 5, as shown, in the middle of an ignition period, reclosing of the power switches will not immediately apply ignition to the burner as the opening of the switches deenergized the solenoid of relay T, causing it to assume the position illustrated and opening the ignition and burner circuits at the terminals 33.

Fig. 2, illustrates another method of obtaining our preignition cycling system of operation and illustrates conventionally the water level contact I, pressure switch 2, fan motor 5, ignition device 1, primer fuel valve 8 and alarm bell 39 as in the form previously described. Fig. 2 does not 11- lustrate the burner motor and main fuel valve but it will be understood that the ignition and alarm mechanism can be applied to various types and arrangements of burners.

The cyclin mechanism in Fig. 2 comprises a shaft 39 driven through the worm and gear 49 from the timer motor 41. The shaft carries an insulating program disk 42, provided with arcuate contacts 43, 44 and 45 arranged to connect the terminals 45, 41, and 48, respectively as will be described presently. The control system is provided with a safety relay indicated in its entirety by the letter T, and a transfer relay indicated in its entirety by the letter R. The flame control switch 49 is for indicating the presence of the flame in the furnace.

The timer motor 41 is arranged to be energized from the conductor 50, either through the terminals 45 and contact 43 on the program disk, or through the terminals 5| closed by one contact of the transfer relay R in the deenergized position of that relay. The solenoid of relay R is arranged to be energized from the dead side of the line through the conductor 52 to terminals 53 positioned on each side of the contact 54 operated by the relay. In the deenergized position of the relay, the terminals 53 are connected to the conductor 55extending to the terminals 55 arranged to be closed in the energized position of the safety relay T. In the energized position of the relay R the terminals 53 are connected through the conductor 51 and normally closed push button switch 58 to the live .side of the line. This later circuit forms a holding circuit to maintain the solenoid of relay R energized so long as the primary switches of the system are closed.

The solenoid of relay T is arranged to be energized through a conductor 59 and a pair of terminals 60 positioned on each side of the contact 51 operated by the relay. In thede-energized position of the relay T the terminals 60 are connected through the conductor 52, flame control switch 49, and terminals 48 to the live side of the line. In the energized position of the relay T, the terminals 60 are connected directly to the live side of the line and complete a holding circuit for the solenoid of relay T.

The alarm bell 39 is connected from the dead side of the line through the conductor 53 to the terminals 64 closed in the energized position of the relay R and returned through the conductor 55 to the previously mentioned conductor 52. The ignition device 1 and the primer fuel valve 8 are connected from the dead side of the line to the conductor 55 and are arranged to be energized by simultaneously closing of the terminals '55 and the terminals 41.

The control system as illustrated in 11:. 2 represents the system in a shut down inoperative condition with the breaker switch 3 and shut down switch 5 open and with the flame control switch 49 closed due to the absence of flame in the furnace. The steps through which the system will operate as shown on starting up the furnace are as follows:

Closing of the breaker switch 3 and shut down switch 5 will immediately energize the fan motor 8 and commence to purge the furnace of any explosive fuel mixture. The timer motor 4i will be energized from the dead side of the line through the conductor 50, terminals 5| on the relay R to the live side of the line. The solenoid of relay T will be energized through the conductor 59, terminals 55, conductor 52, flame control switch 49, and contact 45 on the program disk. Before the program disk has rotated far enough to disengage the terminals 48 the switch arm of relay T will have swung from the position illustrated and sealed itself directly to the line and closed the terminals 56. The circuit to the ignition device and the solenoid of relay R I will remain open at the terminals 41. Continued rotation of the program disk 42 in the direction indicated by the arrow will connect the terminals 45 with the contact 43 completing a running circuit for the motor 4| and opening the terminals 48. After approximately revolution of the program disk the contact 44 will connect the terminals 41, applying energy to the ignition device 1 and primer fuel valve 8 and energizing the solenoid of relay R. The relay R will automatically transfer itself through the terminals 53 and conductor 51 to the live side of the line, and will close the terminals 64 in the alarm bell circuit: however, the alarm bell will not ring due to the opening of the terminals 48 on the program disk. The system will then continue throughout half a rotational cycle of the program disk during which time ignition energy and primer fuel is supplied to the furnace. It will be appreciated that the length of this ignition period may be adjusted by varying the length of the arcuate terminal 44 or the speed of the timer motor 4i.

During the ignition period the main flame should start in the furnace opening the flame control switch 49. When the program disk completes' its single revolution, the terminals 45 will be opened, breaking the circuit to the timer motor and the terminals 48 will be closed as shown. The ignition device 1 will be de-energized at the terminals 41 and the alarm bell circuit will be broken at the flame control switch 49. The furnace will then continue to operate until the power source is broken, either intentionally by the opening of the switch 3 or 5, or by the primary control switches I or 2. The system will revert to the position illustrated and be ready to automatically start a re-light cycle upon reclosing of the main power source.

In the event that the flame does not start by the end of the ignition period, the flame control switch 49 will remain closed when the timer motor is stopped and the terminals 48 are closed. In this position, a circuit will be completed to the alarm bell indicating the need for manual attention of the burner and the attendant may then start the system by opening the push button switch 58. It will be noted that the solenoid of relay R, once energized, remains sealed to the line so long as the primary switches are closed. Opening of the push button switch 58 will deenergize the solenoid of relay R and open the terminals 54, silencing the alarm bell. De-energization oi the relay R will complete the starting circuit to the-conductor ID of the timer motor to start a lighting cycle of the mechanism.

In the event the main flame of the burner should stop for some reason such as clogging of the burner and without the opening of any of the nected to rotate said shaft, a manually control-' primary power switches, the flame control switch 4! will close, sounding the alarm and the system must be restarted manually in the same manner as Just described as after an initial lighting attempt. It should thus be evident that the system illustrated in Fig. 2 will automatically apply a lighting cycle to the furnace upon closing of the primary switches. Should the main power source fail or be cut off during an ignition period and then be reestablished, no ignition energy could be applied due to the opening of the terminals I. on the relay T. The disk would therefore have to continue its unflnished cycle of rotation to the lock-out position illustrated from which position a new and complete cycle of operation would have to be started. As in the other form of the system, the operator's actuation of the push button cannot apply ignition energy to the furnace but can only start the cycling mechanism.

We have thus described two highly practical commercial embodiments of our burner control circuit and mechanism so that others may reproduce the same without further description. We have illustrated two forms of cycling mechanism together with associated relay switches for obtaining delayed operation of the ignition device and it should be understood that we intend these to be examples of a general class of cyclically operating switch mechanism. It should further be understood that the alarm bell illustrated is meant as an example of an indicator generally and could be replaced with a light or other indicating device. Our systems are adaptable to various modes of operation of the burner depending upon the load requirements of the boiler to which they are applied and the desired method of operating the burner. The primary controls illustrated such as the high pressure switch and water level switch are also intended to be repre-- .devices that operate only during the ignition period.

We claim:

l. A control system for the burner of a furnace having a burner motor, comprising a draft fan motor, a primary control element operative responsive to change in a primary operating condition of the furnace, a solenoid operated main fuel valve, a power source including a pair of supply lines, conductors electrically connecting said fan motor across said lines, three cam actuated switches each having one side thereof connected to one of said supply lines, a shaft having cams thereon positioned to open and close said switches in predetermined timed relation, a flrst of said switches being closed whenever a second of the switches is open, a third of said switches being open when said second switch is closed and continuing open a substantial period after the initial closing of the first switch but closing during an 3 ignition period in the later part of the closed period of said first switch, an electric motor conlable circuit connecting said last named motor across said lines for energizing said motor. a holding circuit including said first switch connecting said last named motor across said lines for ener gizing said motor, an electrically operated ignition device and electrically operated primer fuel valve positioned to supply ignition energy and primer fuel to said burner, a pair of flame switches operative responsive to the establishment of a flame in said burner, a relay, an ignition circuit connectable across said lines for energizing said ignition device and opening said primer fuel valve and including in series the third of said cam actuated switches and a first relay switch closed by said relay in the energized condition thereof, a circuit connectable across said lines for energizing said relay and including in series the second of said cam actuated switches, one of said flame switches and a second relay switch closed by said relay in the de-energized position thereof, said one flame switch being closed in the no-flame condition of said burner, a holding circuit connectable across said lines to energize said relay and including a third relay switch closed by said relay in the energized position thereof, an alarm device having an energizing circuit connectable across said lines and through said one flame switch and said second cam actuated switch, a second relay, a circuit for energizing said second relay connectable across said lines and including the second of said flame switches, said second flame switch being closed in the flame operating condition of said burner, a running circuit connectable across said lines to energize said burner motor and said main fuel valve and including a fourth relay switch closed by said second relay in the energized position thereof and said second flame switch, a starting circuit connectable across said lines for energizing said burner motor and said main fuel valve and including a flfth relay switch closed by said second relay in the tie-energized position thereof and said first relay switch and said third cam actuated switch, and a manual switch and an automatic switch adapted to be operated by said primary control element connected in series with one of said lines between the power source and the remainder of the control system.

2. A control system for the burner of a furnace having a burner motor, comprising a draft fan motor, a primary control element operative responsive to change in a primary operating condition of the furnace, a solenoid operated main fuel valve a power source including a pair of supply lines, conductors electrically connecting said fan motor across said lines, three switches each having one side thereof connected to one of said supply lines, cyclically operated mechanism positioned to open and close said switches in predetermined timed relation, a flrst of said switches being closed whenever a second of the switches is open, a third of said switches being open when said second switch is closed and continuing open a substantial period after the initial closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, an electric motor connected to drive said mechanism, a manually controllable circuit connecting said last named motor across said lines for energizing said motor, a holding circuit including said first switch connecting said last named motor across said lines for energizing said motor, an electrically operated ignition device and electrically operated primer fuel valve positioned to supply ignition energy and primer fuel to said burner, a pair of flame switches operative responsive to the establishment of a flame in said burner, a relay, an ignition circuit connectable across said lines for energizing said ignition device and opening said primer fuel valve and including in series the third of said three switches and a first relay switch closed by said relay in the energized condition thereof, a circuit connectable across said lines for energizing said relay and including in series the second of said three switches, one of said flame switches and a second relay switch closed by said relay in the deenergized position thereof, said one flame switch being closed in the noflame condition of said burner, a holding circuit connectable across said lines to energize said relay and including a third relay switch closed by said relay in the energized position thereof, an alarm device having an energizing circuit connectable across said lines and through said one flame switch and said second of said three switches, a second relay, a circuit for energizing said second relay connectable across said lines and including the second of said flame switches,

said second flame switch being closed in the flame operating condition of said burner, a running circuit connectable across said lines to energize said burner motor and said main fuel valve and including a fourth relay switch closed by said second relay in the energized position thereof, a

starting circuit connectable across said lines for energizing said burner motor and said main fuel valve and including a fifth relay switch closed by said second relay in the de-energized position thereof and said first relay switch and said third of said three switches, and a manual switch and an automatic switch adapted to be operated by said primary control element connected in series with said lines between the po er source and the remainder of the control system.

3. A control system for the burner of a furnace having a burner motor, comprisin a power source including a pair of supply lines, three switches each having one side thereof connected to one of said supply lines, cyclically operating mechanism positioned to open and close said switches in predetermined timed relation, a first of said switches being closed whenever a second of the switches is open, a third of said switches being open when said second switch is closed and continuing open a substantial period after the initial closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, an electric motor connected to drive said mechanism, a manually controllable circuit connecting said last named motor across said lines for energizing said motor, a holding circuit including said first switch connecting said last named motor across said lines for energizing said motor, an electrically operated ignition device positioned to supply ignition energy to said burner, a pair of flame switches operative responsive to the establishment of a flame in said burner, a relay, an ignition circuit connectable across said lines for energizing said ignition device and including in series the third of said three switches and a first relay switch closed by said relay in the energized condition thereof, a circuit connectable across said lines for energizing said relay and including in series the second of said three switches, one of said flame switches and a second relay switch closed by said relay in the de- 10 energized position thereof, said one flame switch being closed in the no-iiame condition of said burner, a holding circuit connectable across said lines to energize said relay and including a third relay switch closed by said relay in the energized position thereof, a second relay, a circuit for energizing said second relay connectable across said lines and including the second of said flame switches, said second flame switch being closed in the flame operating condition of said burner, a running circuit connectable across said lines to energize said burner motor and including a fourth relay switch closed by said second relay in the energized position thereof, and a starting circuit connectable across said lines for energizing said burner motor and including a flfth relay switch closed by said second relay in the de energized position thereof and said first relay switch and said third of said three switches.

4. A control system for the burner of a furnace having a burner motor, comprising, a power source including a pair of supply lines, three switches each having one side thereof connected to one of said supply lines, cyclically operating mechanism positioned to open and close said switches in predetermined timed relation, 9, first of said switches being closed whenever a second of the switches is open, a third 01' said switches being open when said second switch is closed and continuing open a substantial period after the initial closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, an electric motor connected to drive said mechanism, a manually controllable circuit connecting said last named motor across said lines for ener izing said motor, a holding circuit icluding said first switch connecting said last named motor across said lines for energizing said motor, an electrically operated ignition device positioned to supply ignition energy to said burner, a flame switch operatively responsive to the establishment of a flame in said burner, a relay, an ignition circuit connectable across said lines for energizing said i nition device and including in series the third of said three switches and a first relay switch closed by said relay in the energized condition thereof, a circuit connectable across said lines for energizing said relay and including in series the second of said three switches, said flame switch and a second relay switch closed by said relay in the de-energized position thereof, said flame switch being closed in the no-flame condition of said burner, a holding circuit connectable across said lines to energize said relay and including a third relay switch closed by said relay in the energized position thereof, an alarm device having an energizing circuit connectable across said lines and Y through said flame switch and said second of said three switches, a primary control element operative responsive to change in a primary operating condition of said furnace, and a manual switch and an automatic switch adapted to be operated by said primary control element connected in series with said lines between the power source and the remainder of the control system.

5. A control system for the burner of a furnace having a burner motor, comprising, a power source including a pair of supply lines, three cam actuated switches each having one side thereof connected to one of said supply lines, a shaft having cams thereon positioned to open and close said switches in predetermined timed relation, a first of said switches being closed whenever a second of the switches is open, a third of said switches beingopen when said second switch is closed and continuing open a substantial period after the closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, an electric motor connected to rotate said shaft, a manually controllable circuit connecting said last named motor across said lines for energizing said motor, a holding circiut including said first switch connecting said last named motor across said lines for energizing said motor, an electrically operated ignition device positioned to supply ignition energy to said burner, a flame switch responsive to the establishment of a flame in said burner, a relay, an ignition circuit connectable across said lines for energizing said ignition device and including in series the third of said cam actuated switches and a, first relay switch closed by said relay in the energized condition thereof, a circuit connectable across said lines for energizing said relay and including in series the second of said cam actuated switches, said flame switch and a second relay switch closed by said relay in the de-energized condition thereof, said flame switch being closed in the no-flame condition of said burner, a holding circuit connectable across said linesto energize said relay and including a third relay switch closed by said relay in the energized position thereof, and an alarm device having an energizing circuit connectable across said lines and through said flame switch and said second cam actuated switch.

6. A control system for the burner of a furnace having a burner motor, comprising, a power source including a pair of supply lines, three cam actuated switches each having one side thereof connected to one of said supply lines, a shaft having cams thereon positioned to open and close said switches in predetermined timed relation, a first of said switches being closed whenever a second of the switches is open, a third of said switches being open when said second switch is closed and continuing open a substantial period after the closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, an electric motor connected to rotate said shaft, a manually controllable circuit connecting said last named motor across said lines for energizing said motor, a holding circuit including said first switch connecting said last named motor across said lines for energizing said motor, an electrically operated ignition device positioned to supply ignition energy to said burner, a flame switch responsive to the establishment of a flame in said burner,

a relay, an ignition circuit connectable across said lines for energizing said ignition device and including in series the third of said cam actuated switches and a first relay switch closed by said relay in the energized condition thereof, a circuit connectable across said lines for energizing said relay and including in series the second of said cam actuated switches, said flame switch and a second relay switch closed by said relay in the de-energized condition thereof, said flame switch being closed in the no-flame condition of said burner, and a holding circuit connectable across said lines to energize said relay and including a third relay switch closed by said relay in the energized position thereof.

7. A burner control system for a furnace having an electrically operated ignition device, comprising, a source of electrical power including a pair of supply lines, first and second relays, three control switches each having one side electriqlly connected to one of said lines, a rotary element positioned to open and close said switches in predetermined timed relation, a first of said switches being open whenever a second of the switches is closed and in the starting position of said mechanism, a third of said switches being open when said second switch is closed and continuing open in the cycle of said element for a substantial period after the closing of the first switch but closing during an ignition period in the latter part of the closed period of said first switch, a, motor connected to drive said rotary element, a circuit connecting said motor across said lines and including in series a first relay switch closed by said first relay in the de-energized position thereof, a holding circuit connectable across said lines in series with said motor and including the first of said control switches, an initial energizing circuit connectable across said lines for energizing said first relay including in series a second relay switch closed by said first relay in the de-energized position thereof and a third relay switch closed by said second relay in the energized position thereof and the third of said control switches, a holding circuit for energizing said first relay connectable across said lines and including in series a fourth relay switch closed by said first relay in the energized position thereof and anormaliy closed manually operable switch, an initial energizing circuit connectable across said lines for energizing said second relay and including in series a fifth relay switch closed by said second relay in the de-energized position thereof and said second control switch, a flame actuated switch closed in response to the absence of a flame in said furnace and connected in series between said fifth relay switch and said second control switch, a holding circuit connectable across said lines to energize said second relay and including in series a sixth relay switch closed by said second relay in the energized position thereof, an alarm device connectable across said lines, the circuit for said device including in series a seventh relay switch closed by said first relay in the energized position thereof, same flame actuated switch and said second control switch, an ignition circuit connectable across said lines to energize said ignition device and including in series said third relay switch and said third control switch, and a second manually operable switch and an automatic switch actuated in response to change in an operating condition of the furnace electrically connected in series in one of said lines between said source and the remainder of the system.

8. A burner control system for a furnace having an electrically operated ignition device, comprising, a source of electrical power including a pair of supply lines, first and second relays, three control switches each having one side electrically connected to one of said lines, a rotary element positioned to open and close said switches in predetermined timed relation, a first of said switches being open whenever a second of the switches is closed and in the starting position of said mechanism, a third of said switches being open when said second switch is closed and continuing open in the cycle of said element for a substantial period after the closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, a motor connected to drive said rotary element, a circuit connecting said motor across said lines and including in series a first relay switch closed by said first relay in the de-energized position thereof, a holding circuit connectable across said lines in series with said motor and including the first of said control switches, an initial energizing circult connectable across said lines for energizing said first relay including in series a second relay switch closed by said first relay in the de-energized position thereof and a third relay switch closed by said second relay in the energized posi tion thereof and the third of said switches, a holding circuit for energizing said first relay connectable across said lines and including in series a fourth relay switch closed by said first relay in the energized position thereof and a, normally closed manually operable switch, an initial energizing circuit connectable across said lines for energizing said second relay and including in series a fifth relay operated switch closed by said second relay in the de-energized position thereof and said second control switch, a, flame actuated switch closed in response to the absence of 'a flame in said furnace and connected in series between said fifth relay switch and said second control switch, a holding circuit connectable across said lines to energize said second relay and in-- cluding in series a, sixth relay switch closed by said second relay in the energized position thereof, an ignition circuit connectable across said lines to energize said ignition device and including in series said third relay switch and said third control switch, and a second manually operable switch and an automatic switch actuated in response to change in an operating condition of the furnace electrically connected in series in one of said lines between said source and the remainder of the system.

9. A burner control system for a furnace having an electrically operated ignition device, comprising, a source of electrical power including a pair of supply lines, first and second relays, three control switches each having one side electrically connected to one of said lines, a rotary element positioned to open and close said switches in predetermined timed relation, a first of said switches being open whenever a second of the switches is closed and in the starting position of said mechanism, a third of said switches being open when said second switch is closed and continuing open in the cycle of said element for a substantial period after the closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, a motor connected to drive said rotary element, a circuit connecting said motor across said lines and including in series a first relay switch closed by said first relay in the de-energ ized position thereof, a holding circuit connectabie across said lines in series with said motor and including the first of said control switches, an initial energizing circuit connectable across said lines for energizing said first relay including in series a second relay switch closed by said first relay in the de-energized position,

thereof and a third relay switch closed by said second relay in the energized position thereof closed in response to the absence of a flame in said furnace and connected in series between said fifth relay switch and said second control switch, a-holding circuit connectable across said lines to energize said second relay and including in series a sixth relay switch closed by said second relay in the energized position thereof, an ignition circuit connectable across said lines to energize said ignition device and including in serlessaid thirdrelay switch and said third control switch, and a shutdown switch electrically connected in series in one of said lines between .said source and the remainder of the system.

10. A burner control system for a furnace hav I ing an electrically operated ignition device, com- :connected to one of said lines, a rotary element positioned to open ani close said switches in predetermined timed relation, a first of said switches being open whenever a second of the switches is closed and in the starting position of said mechanism, a third of said switches being open when said second switch is closed and continuing open in the cycle of said element for a substantial period after the closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, a motor; connected to drive said rotary element, a circuit connecting said motor across said lines and including in series a first relay switch closed by said first relay in the de-energized position thereof, a holding circuit connectable across said lines in series with said motor and including the first of said control switches, an initial energizing circuit connectable across said lines for energizing said first relay including in series a second relay switch closed by said, first relay in the .de-energized position thereof and a third relay switch closed by said second relay in the energized position thereof and 'the third of said control switches, a holding circuit for energizing said first relay connectable across said lines and including in series a fourth relay switch closed by said first relay in the energized position thereof and a normally closed manually operable switch, an initial energizing circuit connectable across said lines for energizing said second relay and including in series a fifth, relay switch closed by said second relay in the de-energized position thereof and said second control switch, a flame actuated switch closed in responsefto the absence of a flame in said furmace and connected in series between said fifth relay switch and said second control switch, a holding circuit connectable across said lines to energize said second relay and including in series a sixth relay switch closed by said second relay in the energized position thereof, and an ignition circuit'connectable across said lines to energize saidig nition device and including in series said third relay switch and said third control switch.

Il. Ab'urner control system for a furnace having an electrically operated ignition device, comprisin a source of electrical power including a pair of supply lines, first and second relays, three control switches each having one side electrically connectedto one of said lines, electrically actuated-"mechanism associated with said control switches to open and close said switches in predetermined timed relation, a first of said switches beingo'pen whenever a second of the switches is closed and in the starting position of said mechanism, a third of said switches being open when said second switch is closed and continuing open in the cycle of said mechanism for a substantial period after the closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, a circuit connecting said mechanism across said lines and including in series a first relay switch closed by said first relay in the tie-energized position thereof, a holdin circuit connectable across said lines in a series with said mechanism and including the first of said control switches, an initial energizing circuit connectable across said lines for energizing said first relay including in series a second relay switch closed by said second relay in the energized position thereof and the third of said control switches, a holding circuit for energizing said first relay connectable across said lines and including in series a third relay switch closed by said first relay in the energized position thereof and a normally closed manually operable switch, an initial energizing circuit connectable across said lines for energizing said second relay and includin in series a fourth relay switch closed by said second relay in the deenergized position thereof and said second control switch, a fiame actuated switch closed in response to the absence of a fiame in said furnace and connected in series between said fourth relay switch and said second control switch, a holding circuit connectable'across said lines to energize said second relay and includin in series a fifth relay switch closed by said second relay in the energized position thereof, an ignition circult connectable across said lines to energize said ignition device and including in series said sec- -ond relay switch and said third control switch,

and a shutdown electrically connected in series in one of said lines between said source and the remainder of the system.

12. A burner control system for a furnace having an electrically operated ignition device, comprising, a source of electrical power including a pair of supply lines, first and second relays, three control switches each having one side electrically connected to one of said lines, electrically actuated mechanism associated with said control switches to open and close said switches in predetermined timed relation, a first of said switches being open whenever a second of the switches is closed and in the starting position of said mechanism, a third of said switches being open when said second switch is closed and continuing open in the cycle of said mechanism for a substantial period after the closing of the first switch but closing during an ignition period in the latter part of they closed period of said first switch, a circuit connecting said mechanism across said lines and including in series a first relay switch closed by said first relay in the de-energized position thereof, a holding circuit connectable across said lines in a series with said mechanism and including the first of said control switches, an initial energizing circuit connectable across said lines for energizing said first relay including in series a second relay switch closed by said second relay in the energized position thereof and the third of said control switches, a holding circuit for energizing said first relay connectable across said lines and including in series 'a third relay switch closed by said first relay in the energized position thereof and a normally closed manually operable switch, an initial energizing circuit connectable across said lines for energizing said second relay and including in series a fourth relay switch closed by said second relay in the deenergized position thereof and said second control switch, a flame actuated switch closed in response to the absence of a fiame in said furnace and connected in series between said fourth relay switch and said second control switch, a holding circuit connectable across said lines to energize said second relay and including in series a fifth relay switch closed by said second relay in. the energized position thereof, and an ignition circuit connectable across said lines to energize said ignition device and including in series said second relay switch and said third control switch.

13. A control system for the burner of a furnace having a primary control element operatively responsive to change in a primary operating condition of a furnace, and an electrically operated ignition device, comprising a source of electrical power including a pair of supply lines, a relay, three control switches each having one side electrically connected to one of said lines, electrically actuated mechanism associated with said control switches to open and close said switches in predetermined timing relation, a first of said switches being open whenever a second of the switches is closed and in the starting position of said mechanism, a third of said switches bein open when said second switch is closed and continuing open in the cycle of said mechanism for a substantial period after the closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, a manually controllable initial energizing circuit connecting said mechanism across said lines, a holding circuit connectable across said lines in series with said mechanism and including the first of said control switches to energize said mechanism to the end' of its cycle independently of said manually controllable circuit, an initial energizing circuit for said relay connectable across said lines and including in series said second of said control switches and a relay switch closed by said relay in the de-energized position thereof, a flame switch operativeiy responsive to the establishment of fiame in said burner and connected in series with said second control switch in the initial energizing circuit of said relay, said flame switch being arranged to close in the no-fiame conditions of said burner, a holding circuit for energizing said relay connectable across said lines and including in series a second relay operated switch closed by said relay in the energized position thereof, an igni tion circuit connectable across said lines to energize said ignition device and including in series a third relay operated switch closed by said relay in the energized position thereof and said third of said control switches, an alarm device connectable across said lines, the circuit for said device including in series said fiame switch and said second control switch, and an automatic switch adapted to be operated by said primary control element connected in series in one of said lines between said source and the remainder of the system.

14. A control system for the burner of a furnace having a primary control element operatively responsive to change in a primary operating condiiton of a furnace and an electrically operated ignition device, comprising, a source of electrical power including a pair of supply lines, a relay, three control switches each having one side electrically connected to one of said lines, electrically actuated mechanism associated with said control switches to open and close said switches in predetermined timing relation, a first of said switches being open whenever a second of the switches is closed and in the starting position of said mechanism, a third 01' said switches being open when said second switch is closed and continuing open in the cycle of said mechanism for a substantial period after the closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, a manually controllable initial energizing circuit connecting said mechanism across said lines, a holding circuit connectable across said lines in series with said mechan smand including the first oi. said control switches to energize said mechanism to the end of its cycle independently or said manually controllable circuit, an initial energizing circuit for said relay eonnectable across said lines and including in series said second of said control switches, a fiame switch operatively responsive to the establishment of flame in said burner and connected in series with said second control switch in the initial energizing circuit of said relay, said fiame switch being arranged to close in the no-fiame condition-of said burner, a holding circuit for energizing said relay connectable across said lines and including in series a first relay operated switch closed by said relay in the energized position thereof, an ignition circuit connectable across said lines to energize said ignition device and including in series a second relay operated switch closed by said relay in the energized position thereof and said third of said control switches, and an automatic switch adapted to be operated by said primary control element connected in series in one of said lines between said source and the remainder of the system.

15. A control system for the burner 01 a furnace having an electrically operated ignition device, comprising, a source of electrical power including a pair of supply lines, a relay, three control switches each having one side electrically connected to one of said lines, electrically actuated mechanism associated with said control switches to open and close said switches in predetermined timing relation, a first of said switches being open whenever a second oi the switches is closed and in the starting position oi said mechanism, a third or said switches bein open when said second switch is closed and continuing open in the cycle or said mechanism for 18 a substantial period after the closing of the first switch but closing during an ignition period in the later part of the closed period of said first switch, a manually controllable initial energizing circuit connecting said mechanism across said lines, a holding circuit conneetable across said lines in series with said mechanism and including the first of said control switches to energize said mechanism to the end of its cycle independently of said manually controllable circuit, an initial energizing circuit for said relay connectable across said lines and including in series said second of said control switches, a. flame switch operatively responsive to the establishment of flame in said furnace and connected in series with said second control switch in the initial energizing circuit of said relay, said flame switch bein arranged to close in the no-fiame condition of said burner, a holding circuit for energizing said relay eonnectable across said lines and including in series a first relay operated switch closed by said relay in the energized position thereof, an ignition circuit connectable across said lines to energize said ignition device and including in series a second relay operated switch closed by said-relay in the energized position thereof and said third of said control switches, and a shutdown switch connected in series in one of said lines between said source and the remainder of the system.

HOMER C. NYCUM. CLYDE O. BAIRD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,674,051 McCabe, June 19, 1928 1,877,037 Parker Sept. 13, 1932 1,961,802 Taylor June 5, 1934 2,021,647 DeLancey Nov. 19, 1935 2,297,821 Whempner Oct. 6, 1942 2,388,666 Bower Nov. 13, 1945 2,425,589 Aubert Aug. 12, 1947 2,472,398 Berger June 7, 1949 2,501,452 Pratt Mar. 21, 1950 

